package com.lqk.server;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.*;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;

/**
 * 聊天室-服务器端
 */
public class ChatServer {

    /*
        服务器端启动的方法
     */
    public void startServer() throws Exception {
        // 1 创建Selector选择器
        Selector selector = Selector.open();
        // 2 创建ServerSocketChannel通道
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        // 3 为channel通道绑定监听端口
        serverSocketChannel.bind(new InetSocketAddress(8000));
        // 通道设置为非阻塞模式
        serverSocketChannel.configureBlocking(false);
        // 4 把channel注册到selector
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服务器已经启动成功了");
        // 5 循环，等待有新的连接接入
        //相当于while(true)
        for (;;){
            // 获取channel数量
            int readChannels = selector.select();

            if (readChannels==0){
                continue;
            }
            // 获取可用的channel
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            // 遍历
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            while (iterator.hasNext()){
                SelectionKey selectionKey = iterator.next();
                //移除set集合中当前selectionKey
                iterator.remove();
                // 6 根据就绪状态，调用对应方法实心具体业务操作
                // 6.1 如果是accept状态
                if (selectionKey.isAcceptable()){
                    acceptOperator(serverSocketChannel,selector);
                }
                // 6.2 如果是可读状态
                if (selectionKey.isReadable()){
                    readOperator(selector,selectionKey);
                }
            }
        }


    }

    // 处理可读状态操作
    private void readOperator(Selector selector, SelectionKey selectionKey) throws Exception {
        // 1 从SelectionKey获取到已经就绪的通道
        SocketChannel socketChannel = (SocketChannel) selectionKey.channel();
        // 2 创建Buffer
        ByteBuffer byteBuffer=ByteBuffer.allocate(1024);
        // 3 循环读取客户端消息
        int readLength = socketChannel.read(byteBuffer);
        String message="";
        if (readLength>0){
            // 切换为读模式
            byteBuffer.flip();
            // 读取内容
            message += Charset.forName("UTF-8").decode(byteBuffer);
        }
        // 4 将channel再次注册到选择器上，监听可读状态
        socketChannel.register(selector,SelectionKey.OP_READ);
        // 5 把客户端发送的消息，广播到其他客户端
        if (message.length()>0){
            // 广播给其他客户端
            System.out.println(message);
            castOtherClient(message,selector,socketChannel);
        }
    }

    // 广播给其他客户端
    private void castOtherClient(String message, Selector selector, SocketChannel socketChannel) throws IOException {
        // 1 获取所有已经接入的客户端
        Set<SelectionKey> selectionKeySet = selector.keys();
        // 2 循环像所有channel广播消息
        for (SelectionKey selectionKey:selectionKeySet) {
            //获取每个channel
            Channel targetChannel = selectionKey.channel();
            //将自己排除，不需要给自己发送
            if (targetChannel instanceof SocketChannel && targetChannel != socketChannel){
                ((SocketChannel)targetChannel).write(Charset.forName("UTF-8").encode(message));
            }

        }

    }

    // 处理接入状态操作
    private void acceptOperator(ServerSocketChannel serverSocketChannel, Selector selector) throws Exception {
        // 1 接入状态，创建socketChannel
        SocketChannel socketChannel = serverSocketChannel.accept();
        // 2 将socketChannel设置为非阻塞模式
        socketChannel.configureBlocking(false);
        // 3 将socketChannel注册到selector，监听可读状态
        socketChannel.register(selector,SelectionKey.OP_READ);
        // 4 客户端回复信息
        socketChannel.write(Charset.forName("UTF-8").encode("欢迎进入聊天室，请注意隐私安全！"));
    }

    // 启动的主方法
    public static void main(String[] args) {
        try {
            new ChatServer().startServer();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}
